Modelling plasticity of Ni3Al-based L1(2) intermetallic single crystals. I. Anomalous temperature dependence of the flow behaviour

A comprehensive mechanism-based crystallographic constitutive model has been developed for L1(2)-structured Ni3Al-based intermetallic single crystals. This model represents the unusual thermomechanical behaviours of Ni3Al, such as the anomalous temperature dependence of both the flow stress and strain-hardening rate (SHR), the strain dependence of these anomalous behaviours and an orientation-dependent tension - compression asymmetry. The model framework was based on two major contributions to plastic flow, namely the repeated cross-slip exhaustion and athermal defeat of screw-character dislocations, and the motion of macro-kinks (MKs). The contribution of irreversible obstacle storage was incorporated into the constitutive formulations as a resistance against the glide of MKs. The model was implemented in a finite element method numerical framework, and the simulation results showed qualitative agreement with experimental observations.